1. Field of the Invention
This invention relates to a stepless or continuously variable automatic transmission to be mounted between an engine and a drive wheel axle of a motor vehicle.
2. Description of the Prior Art
The front-engine/front-drive type motor vehicles have come to employ a stepless automatic transmission which has its power transmission shaft divided into three parts as shown in FIG. 1 for the purpose of reducing its axial dimension from the standpoint of improving the mountability of the transmission. As seen in the figure, a first shaft 100 which is disposed coaxially with the engine output shaft is provided with an input pulley 52. A second shaft 200 which is disposed parallel with the first shaft is provided with an output pulley 56 and an output gear 59 at its output end, the second shaft 200 being supported at three points by the transmission case including a torque converter case, transmission case and an center case for ensuring rigidity of the shaft. The third shaft 81 is disposed parallel with the second shaft and provided with a speed-recuding idler gear. In such conventional transmission, the second shaft is constituted by a unitary shaft with an output pulley 56 and an output gear 59, so that it requires high concentricity of the bearings to be mounted at the three supporting points, necessitating simultaneous machining of the bearings to improve the accuracy of the machining of the machining operation. This is obviously reflected by low productivity and high production cost.